The invention relates to a process and equipment for the treatment of liquid/solids mixtures, in particular for the conditioning of suspended solids by means of cavitation.
The boiling point of liquids is strongly dependent on pressure. The boiling temperature drops with decreasing pressure. Under strong vacuum, such as may occur at high velocities, or when ambient pressure drops, pressure can decrease locally to boiling pressure. Such conditions frequently occur in hydrodynamic flow machines, such as pumps, turbines, propellers, for instance when turbine blades are passed, etc. This results in what is know as cavitation. In it, vapour and gas-bubbles are released from the liquid and cause the formation of voids. A subsequent pressure rise is accompanied by rapid collapse of the bubbles, so-called impact condensation (E. Truckenbrodt, "Steuerungsmechanik", Springer Verlag 1968, Page 15 or Dubbel "Taschenbuch fur den Maschinenbau", Springer Verlag 1983, Page 893).
Although this phenomenon is in many cases undesirable owing to the possiblity of erosion of the material around which flow takes place, and also due to the considerable noise caused by cavitation, it may be usefully applied in other cases, in particular, for instance, as an aid in the destruction of germs in waste water. DE-PS 24 55 633 deals with this.
In this known process such an amount of sonic energy is introduced into the water in zones with a sufficient ozone concentration for the destruction of germs that cavitation occurs, permitting the attainment of an increase in the germicidal effects of the ozone in the waste water. These familiar means of generating cavitation by means of sonic energy involve a high degree of equipment complexity and investment. A method is also known of generating cavitation by means of a cavitator, which can essentially be compared to a centrifuge. This is also a relatively complex and expensive solution.